I recently tried building an example project that included both derelict-sdl2 and derelict-gl3, and dub was unable to resolve their dependencies because they didn't match (gl3 wanted >=1.0.3 and sdl2 wanted ~>2.0.4.) Two problems with this:

First, dub should be able to resolve this dependency. >=1.0.3 and ~>2.0.4 should be able to be resolved to the same version of derelict-util, but for some reason that doesn't happen.

Second, the error message given was
"Unresolvable dependencies to package derelict-util:
  derelict-gl3 1.0.24 depends on derelict-util >=1.0.3
  derelict-sdl2 2.1.4 depends on derelict-util ~>2.0.4".
This error message doesn't make it clear that the problem is a version conflict, and doesn't inform the user about how to resolve the problem. A better error would be something along the lines of "Dependencies to package derelict-util could not be resolved because the following packages depend on incompatible versions of it: [LIST OF PACKAGES HERE].

I ended up having to change the dub.json of derelict-gl3 to resolve this issue.